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LearnCambridge97022025–2027Paper 2 · AS Level Structured QuestionsWork, energy and power

Paper 2 · Module

Work, energy and power

2 subtopics≈ 70 min in total

Start the module: Work, power and efficiency Open graphing calculator

Work, power and efficiency
Work is done when a force moves its point of application: $W=Fs\cos\theta$ , the force times the displacement in its direction. It's the area under a force–displacement graph, and $W=p\Delta V$ for a gas expanding at constant pressure. Power is the rate of doing work: $P=\dfrac Wt$ , and for a force moving at steady speed, $P=Fv$ . Efficiency compares useful output with total input.
≈ 35 min
Kinetic and potential energy
Kinetic energy $E_k=\tfrac12mv^2$ comes from the work done to accelerate a mass from rest. The change in gravitational potential energy near the Earth is $\Delta E_p=mg\Delta h$ , from the work done lifting it. Energy problems become bookkeeping: initial energy $=$ final energy $+$ energy dissipated against friction.
≈ 35 min